The present invention will be described in relation with plasma display panel. A plasma display panel utilises a matrix array of discharge cells, which could only be switched ON or OFF. Also unlike a CRT or LCD in which grey levels are expressed by analogue control of the light emission, in a PDP, modulating the number of light pulses per frame controls the grey level. The eye will integrate this time-modulation over a period corresponding to the eye time response.
For static pictures, this time-modulation, repeats itself, with a base frequency equal to the frame frequency of the displayed video norm. As known from the CRT-technology, a light emission with base frequency of 50 Hz, introduces large area flicker, which can be eliminated by field repetition in 100 Hz CRT TV receivers.
Contrary to the CRTs, where the duty cycle of light emission is very short, the duty cycle of light emission in PDPs is ˜50% for middle grey. This reduces the amplitude of the 50 Hz frequency component in the spectrum, and thus large area flicker artefact, but due to the larger size of PDPs, with a larger viewing angle, even a reduced large area flicker becomes objectionable in terms of picture quality. The present trend of increasing size and brightness of PDPs, will also contribute to aggravate this problem in the future.
To avoid the large area flicker artefact in PDPs, a specific video processing method has been proposed in EP patent application Nr 0982708 in the name of Deutsche Thomson Brandt. The method that will be described hereafter more in detail, consists of optimising sub field organisation for the frame period. The sub-fields of a frame are organised in two consecutive sub-fields groups and to a value of a pixel, a code word is assigned, which distributes the active sub-field periods equally over the two sub-fields groups. If this solution is optimised for so-called camera mode sources, specific optimisation can be realized to improve the overall picture performance, in case of film mode sources.